Use eigen blas for blas routines (#2672)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/2672

In previous diffs we added eigen_blas for accelerating blas routines. In this
diff we enable linking it for llama runner
ghstack-source-id: 220378204
exported-using-ghexport

Pre-existing lint failures
bypass-github-export-checks
bypass-github-pytorch-ci-checks

Reviewed By: digantdesai, mcr229

Differential Revision: D55344019

fbshipit-source-id: e76c71c36d8f0044c7c26364ec136aa7ed963544